1. Field of the Invention
The present invention generally relates to data management methods and apparatuses, hierarchical storage apparatuses and computer-readable storage media, and more particularly to a data management method and a data management apparatus for managing data in a library apparatus using recording media other than hard disks, such as magnetic tapes, and to a hierarchical storage apparatus which is hierarchically formed by a hard disk apparatus and a library apparatus and employs such a data management method, and to a computer-readable storage medium which stores a program for causing a computer to function as a data management apparatus.
2. Description of the Related Art
Conventionally, large-capacity information file (or storage) systems are mainly library apparatuses which use recording media such as magnetic tapes and optical disks. However, such a library apparatus require time to exchange information with a host computer in order to carry out read and write processes. For this reason, the library apparatus is not used as an information storage apparatus for on-line access use, but used mainly as a backup apparatus. On the other hand, a high-speed access can be made with respect to a hard disk apparatus, but the cost of the hard disk is high compared to that of a magnetic tape and the like. Consequently, it is difficult to realize an inexpensive large-capacity information file system by solely using the hard disks.
Hierarchical information file systems formed by a hard disk apparatus that is connected to a library apparatus using magnetic tapes have been proposed based on the so-called Information Lifecycle Management (ILM). However, such hierarchical information file systems are designed to automatically backup the information stored in the hard disks, and the user must be fully aware of the library apparatus which uses the magnetic tapes.
In addition, techniques have been proposed to efficiently manage the hierarchical information file system by a management software of the host computer, but the user still needs to be fully aware of the library apparatus which uses the magnetic tapes. Furthermore, there was an inconvenience in that the information access by the application program puts pressure on the network resources.
A data management system proposed in a Japanese Laid-Open Patent Application No.9-26904 copies data having a high frequency of use from a storage medium of the library apparatus to the hard disk in advance. If the requested data is not recorded in the hard disk, the requested data is not output directly from the library apparatus, but is output after being copied and recorded in the hard disk. Hence, the data request from each application program is processed separately from the library apparatus, and the data management system carries out a control as if all of the data are recorded in the hard disk. In this proposed data management system, the library apparatus is virtually used as a portion of the hard disk apparatus.
When virtually using the library apparatus as a portion of the hard disk apparatus, the user must manage each recording medium within the library apparatus, that is, manage each volume. In other words, since the recording media of the library apparatus are loaded and unloaded (or mounted and demounted), the use must always manage the volumes. However, when using the library apparatus, a multi-file volume may be employed in which a plurality of files are recorded in one volume or, a multi-volume file may be employed in which one file is recorded in a plurality of volumes.
Conventionally, when virtually using the library apparatus as a portion of the hard disk apparatus, the volumes must be managed by the user. For this reason, there were problems in that the user must carry out the troublesome operation of managing the volumes, and that the user must always be fully aware of the library apparatus.